Thanks for the pointer, but it doesn’t specifically mention port 237. I mean, what services uses it? I have a Kopano server, with users accessing via z-push, outlook+activesync+koe, webapp/deskapp, imap. But I seen absolutely no traffic to port 237 when monitoring with iptables. So for what exactly is port 237 needed? Can I close it?

Thanks for clearing that up. That means there is no reason to have either 236 or 237 open, unless you use the old Zarafa mapi client, or if you happen to have to use the old zarafa-pst-migration tools. I think the documentation should mention this, no need to have unused ports open.

@klausade you were just as unspecific in your question, as I was in my answer

Apart from the obvious “the old mapi client uses it”, it is also being used for services to communicate between each other, if you have a distributed setup with components on multiple devices (or you’re running kopano-admin on a different machine, for example). The standard use case is that all services are running on the same machine, therefore these ports don’t have to be open to the public anymore.